Road Sign Math

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Genesis

March 8th, 2005 · 5 Comments

MinnesotaExemplary Sign

“Almost everything comes from nothing.” — Henry F. Amiel

Everything has a beginning, including Road Sign Math. I have travelled on I-94 many times. If you are unfamiliar I-94 is the only interstate that crosses through my home state of North Dakota. Like most roads in North Dakota it is straight as an arrow cutting directly east-to-west making stops in Bismarck, Jamestown and Fargo. I have a number of relatives in North Dakota so I end up taking this route at least a couple of times a year. Heading east on I-94 the beginning of Road Sign Math was discovered in the Minnesota segment of I-94 just 99 miles outside of Minneapolis.

The first time I saw this sign the math stunned me. It seemed so obvious and straightforward. I was surprised to not see a designated area to pull-off the side of the road and take a picture like some sort of scenic overlook or historic landmark. There should have been a line of cars observing this unique oddity. The math of the sign follows directly from top to bottom, like a problem in a 3rd grade text on multiplication.

3 \times 33 = 99

I saw this sign a few times and I would always remark to myself about it. I would wonder how many other signs there were like it. I would wonder, are there other signs that have such mathematical relevance? Is this some oddity, something that is unique to this one spot in the country? It really can’t be the only one, right? Have pity on the poor souls that happened to be in the passenger seat when passing this sign and hearing me go on and on about it.

This sign was the only one that I saw for years. Then, without even really looking for it I saw a second sign (hint: it is on I-35 South towards Minneapolis and has not been posted yet). All of a sudden I knew that there had to be more and only a few short weeks after that Road Sign Math was born.

This sign was captured thanks to my mother without requiring me to drive 200 miles round trip and get it on I-94 eastbound towards Minneapolis just after mileage marker 133. The GPS coordinates are approximately N45 41 18.4 W94 51 51.2. See sign on map!

Tags: Minnesota

5 responses so far ↓

  • 1 John Murphy // Mar 20, 2005 at 4:00 pm

    Here’s something interesting to consider. I noticed that the class of signs you cite in this example are quite common as you drive though the midwest. The characteristic of the class is that there are positive three numbers on a sign, in increasing magnitude of distance, in this case, 3, 33, and then 99. Let’s call our three numbers n1, n2, and n3. For all signs where n3 > |n1 - n2|, I can proove there exists at least one polynomial function that when plotted on a cartesian coordinate system with n1, and n2 being points on the x axis, that n3 will be the area of the region bounded by the polynomial and the first two numbers. Lets take the linear case. In this case take the definite integral of f(x) = (1/50)x + 147/50 bounded by 3 and 33, the answer is 99.

  • 2 Road Sign Math // Mar 20, 2005 at 4:43 pm

    Don’t go trying to ruin my math fun with your liberal elite polynomial riddles! Trying to sound all smart with your cardinal this and cartesian that… I just want to have my reward…

    Driving + Math = Fun!

    :-)

  • 3 Doh! // Nov 3, 2005 at 1:27 pm

    Looks like someone has used your photo as part of one of those internet puzzles …

    http://www.cerebral-x.com/game/road_signs.htm

  • 4 Froggie // Dec 3, 2005 at 8:38 pm

    In response to John Murphy, one problem that will blow your theory clear out of the water comes with signs that show a greater mileage in the middle than the one on the bottom. Rare, but they do exist (usually due to contractor error or someone at the DOT smoking some good stuff).

  • 5 Genry Henz // Feb 2, 2006 at 7:45 am

    not bad

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